Do you know off any app that i can use with my kinect ( for xbox) and windows 8?
The Kinect for Windows SDK works great with Windows 8 desktop apps. If you just want to have some fun, download the Kinect for Windows SDK and the Kinect for Windows SDK Toolkit which includes a number of pre-built apps that you can play with. That said, you cannot use Kinect in a Windows Store app, with the exception of using an intermediary PC and using the network, with a project like this - http://kinectservice.codeplex.com/
Download the SDK and Toolkit - Note: Some demos require additional software to be installed, like if you're using the XNA Avatar demo, you need to install XNA. Just follow the instructions for each demo and you'll be good.
Hope this helps,